Best Ultralight Backpack: 8 Packs Compared by Weight, Comfort, and Price

The average ultralight backpack weighs around two pounds, holds 55-60 liters, and comfortably carries 30-35 pounds. That’s a massive improvement over the 5-6 pound traditional packs most hikers start with. But picking the right one means understanding the tradeoffs between weight, comfort, durability, and price — because cutting ounces in the wrong places creates problems on the trail.

After researching thru-hiker feedback, gear testing data, and community discussions, here are the eight best ultralight backpacks available right now, organized by what each one does best.

Quick Comparison Table

Best Framed Ultralight Backpacks

1. Gossamer Gear Mariposa 60 — Best Transition Pack

The Mariposa has been the gateway drug into ultralight backpacking for years, and for good reason. It offers virtually all the utility of a traditional backpack — large mesh side pockets, a hipbelt with pockets, compression straps, load lifters — at a fraction of the weight. If you’re coming from a 4-5 pound pack and nervous about losing features, the Mariposa removes that anxiety.

The “frame” is a removable sit pad (SitLight pad) that doubles as a back panel stiffener. This gives the pack enough structure to carry 30 pounds comfortably while keeping overall weight at 1 lb 11 oz. Remove the pad at camp and you’ve got a seat for cooking or hanging out.

Why hikers pick it: Full feature set at ultralight weight. You don’t have to change your packing habits. Tradeoff: The Robic nylon fabric is durable but not waterproof — you’ll need a pack liner or rain cover. Best for: Hikers transitioning from traditional packs, 3-season trips, anyone who wants pockets and organization.

2. Hyperlite Mountain Gear Southwest 55 — Best Durability

HMG builds the Southwest from Dyneema Composite Fabric (DCF), which is simultaneously waterproof, tear-resistant, and light. This is the pack that thru-hikers choose when they want something that will survive 2,000+ miles of abuse without developing holes, tears, or delamination.

The internal aluminum stays transfer weight to the hipbelt effectively, and the roll-top closure with a Y-strap system provides solid compression. The Southwest handles 35 pounds without sagging, which gives you headroom for water carries in dry sections or packing extra layers in shoulder seasons.

Why hikers pick it: Bomber construction that doesn’t sacrifice weight. Waterproof without a liner. Tradeoff: Most expensive option on this list. The white DCF shows dirt quickly (cosmetic, not functional). Best for: Thru-hikers, wet climates, rough trail conditions, anyone hard on gear.

3. Zpacks Arc Haul Ultra 60 — Lightest Framed Pack

At 1 lb 5 oz with a full carbon fiber external frame, the Arc Haul Ultra defies expectations. The external frame creates a trampoline-style suspended back panel that provides ventilation and weight transfer simultaneously. Load lifters and a contoured hipbelt give this pack a carrying comfort that approaches much heavier packs.

The 40-pound max load rating is the highest on this list for a framed ultralight pack, making the Arc Haul Ultra viable for longer resupply intervals or winter trips where you’re carrying extra insulation and fuel.

Why hikers pick it: Best weight-to-carry-capacity ratio available. Carbon frame is remarkably effective. Tradeoff: Carbon fiber is stiff but can break under point impact (sitting on it with a rock underneath). Ultra 200 fabric is durable but not as tough as Dyneema. Best for: Experienced ultralight hikers who want framed comfort at frameless weight.

4. REI Co-op Flash Air 50 — Best Value

The Flash Air 50 is REI’s entry into the ultralight market, and it punches well above its $199 price point. The hourglass-shaped spring-steel frame provides real structure and weight transfer, the hipbelt wraps properly, and the backpanel offers moderate breathability. After testing across trails from Minnesota to Texas, reviewers consistently praise how well it carries for its weight class.

At just under 2 pounds, it’s the heaviest pack on this list, but it’s also $100-200 cheaper than the competition. If you’re not ready to commit $350+ to an ultralight pack, the Flash Air lets you experience the category without the premium price.

Why hikers pick it: Real ultralight performance at a mainstream price. Available at REI stores to try on. Tradeoff: Slightly heavier than dedicated UL brands. Fewer customization options. Best for: Budget-conscious hikers, first-time ultralight buyers, anyone who wants to try before buying.

5. Six Moon Designs Swift X — Best All-Rounder

After 1,000 miles and a year of field testing, the Swift X has earned recognition as one of the most well-rounded ultralight packs available. The carbon fiber stays provide structure without excessive weight, and the overall design balances carrying comfort, pocket access, and durability better than most competitors at this weight.

The 50L capacity is sufficient for most three-season trips with an ultralight kit. The Swift X doesn’t excel in any single category — it’s not the lightest, cheapest, or most durable — but it has the fewest compromises overall.

Why hikers pick it: No significant weaknesses. Does everything well. Tradeoff: Jack of all trades means it’s not the best at any single thing. Best for: Hikers who want a reliable do-everything pack without overthinking the decision.

6. Outdoor Vitals CS40 Ultra — Best Load Transfer

The CS40 Ultra prioritized the frame and suspension system, and it shows. Thru-hiker Sam Schild, who has tested over 20 backpacking packs in a single year, stated that the CS40 Ultra carries weight the best out of all of them. At 40L, it’s sized for hikers with a dialed-in kit who know exactly what they carry.

The internal frame transfers load to the hipbelt with an efficiency that larger, heavier packs struggle to match. If you’ve ever had hip soreness or shoulder fatigue from an ill-fitting pack, the CS40 Ultra’s suspension system is worth investigating.

Why hikers pick it: Superior weight transfer for a pack this light. Comfortable with heavier loads. Tradeoff: 40L is tight for longer trips or if your sleep system is bulky. Smaller brand with less availability. Best for: Experienced hikers with a refined kit who prioritize carry comfort.

Best Frameless Ultralight Backpacks

Frameless packs are for hikers whose total pack weight (base weight + consumables) stays under 20-25 pounds. If your base weight is above 12-15 pounds, a framed pack will be significantly more comfortable.

7. Gossamer Gear G4-20 — Best Frameless for Beginners

The G4-20 is a 42L frameless pack that weighs 24.8 oz and comfortably handles loads up to 25 pounds. For a frameless design, 25 pounds is impressive — most frameless packs tap out around 20. The extra capacity comes from Gossamer Gear’s padding and the way the pack distributes weight across your back.

The 42L volume also gives more room than typical frameless packs, which tend to sit in the 30-38L range. If you’re interested in frameless but not ready to go full minimalist with your packing, the G4-20 bridges the gap.

Why hikers pick it: Most forgiving frameless pack. Handles more weight and volume than competitors. Tradeoff: Heavier than ultralight frameless options. Not waterproof. Best for: Hikers curious about frameless carrying who want a safety margin.

8. Zpacks Nero Ultra 38L — Lightest Pack Period

At 10.3 ounces, the Nero Ultra is barely heavier than a water bottle. The Ultra 100 fabric is waterproof and seam-taped, so you don’t need a pack liner. The roll-top closure provides volume flexibility, and the simple design means there’s very little that can break or fail on trail.

This is a pack for hikers who have spent years refining their kit down to the essentials. With a 20-pound max load and no frame, you need a base weight under 10 pounds to carry this comfortably with food and water.

Why hikers pick it: Barely there on your back. Waterproof without a liner. Tradeoff: No frame means no load transfer — all weight sits on your shoulders. 20 lb max is firm. Best for: Sub-10 lb base weight hikers, fastpackers, minimalist thru-hikers.

How to Choose the Right Ultralight Pack

Step 1: Know your base weight

Your base weight (everything except consumables like food, water, and fuel) determines whether you need a frame:

• Base weight 15+ lbs: Get a framed pack. The Mariposa 60 or Flash Air 50 are forgiving choices.
• Base weight 10-15 lbs: Either framed or frameless works. The Swift X or G4-20 sit in this sweet spot.
• Base weight under 10 lbs: Frameless packs shine here. The Nero Ultra or G4-20 are ideal.

Step 2: Match capacity to trip length

• Overnight / 1-2 nights: 35-45L
• 3-5 day trips: 45-55L
• Thru-hiking / 5+ days between resupply: 55-65L

These assume an ultralight kit. If your sleeping bag compresses to the size of a football and your shelter is a tarp or single-wall tent, you can go smaller. If you’re carrying a 2-person tent and a synthetic sleeping bag, size up.

Step 3: Consider your conditions

• Wet climates (Pacific Northwest, Scotland, New Zealand): Prioritize waterproof materials. HMG Southwest or Zpacks Nero Ultra eliminate the need for a pack liner.
• Rough trails (off-trail, bushwhacking, scrambling): Durability matters. HMG Southwest’s Dyneema handles abrasion better than any other option here.
• Desert / dry climates: Ventilation matters more than waterproofing. The Arc Haul Ultra’s suspended back panel or the Flash Air 50’s mesh panel keep sweat manageable.

Step 4: Try it on if possible

Fit matters more than specs. A pack that fits your torso length and hip shape will carry 25 pounds better than a “superior” pack that doesn’t sit right. REI stocks the Flash Air 50 in stores. Gossamer Gear and HMG have good return policies. Some outdoor gear shops stock cottage industry packs.

Common Ultralight Backpack Mistakes

Buying too small. A pack that’s too small leads to strapping gear on the outside, which throws off balance, catches on branches, and exposes gear to rain. Better to have 5L of extra space than to strap your tent to the outside.

Ignoring hipbelt fit. An ultralight pack with a good hipbelt transfers 60-70% of the load to your hips. Without a properly fitting hipbelt, all weight goes to your shoulders. Most cottage brands offer multiple hipbelt sizes — measure and pick the right one.

Skipping the pack liner. Unless your pack is waterproof (HMG, Zpacks with DCF), use a trash compactor bag as a pack liner. It weighs 1.5 oz and protects everything inside. A wet sleeping bag on a cold night is a safety issue, not just a comfort one.

Overloading a frameless pack. Frameless packs work brilliantly within their load limits and terribly beyond them. If your total pack weight regularly exceeds 25 pounds, get a framed pack and enjoy the trip instead of fighting your gear.

The Weight Savings Add Up

Switching from a traditional 5-pound pack to a 2-pound ultralight pack saves 3 pounds. That doesn’t sound dramatic until you add it to the rest of an ultralight kit: lighter tent (-2 lbs), lighter sleeping bag (-1 lb), lighter pad (-0.5 lb). Suddenly you’ve cut 6-7 pounds, which translates to more miles per day, less joint stress, and more energy at camp.

The backpack is usually the single biggest weight savings you can make. It’s the right place to start your ultralight journey.